Then run "update-mime-database ~/.local/share/mime" to update your mimetypes database.

2. Add an icon

Grab an icon from here, and save it as ~/.icons/x-extension-ifc.png (or /usr/share/icons/x-extension-ifc.png for system-wide). Now your file manager should display IFC files a bit more nicely:

3. Open IFC files

There are currently no applications that can save ifc files (might change sooner than you think, however), but there are already a couple of solutions to open them. The following example is taken from the buildingSmart examples page ((Duplex model):

FreeCAD: Can open IFC file with its internal parser (not all entiites are supported and, starting from version 0.13 (to be released soon), is able to use IfcOpenShell if it is installed on your system, and with it, can import the whole contents of an IFC file:

OpenIfcTools: Has a javawebstart viewer, simple but very good for quickly inspecting IFC files:

Blender: Can also open ifc files when IfcOpenShell and its blender importer addon are installed. Although it uses the same IFC import engine, the file import operation is much faster than FreeCAD, because the mesh data that blender uses is much quicker to construct than FreeCAD's more complex parametric objects:

BimServer: The BimServer is a multiplatform server application, made to share, review and maintain IFC-based projects. It has several interesting functionalities such as conversion to/from several other formats, cobie support, revision control, etc... It has also a WebGL viewer program for it (called BimSurfer), which can render a the project in WebGL (3D inside your web browser):

5. Save IFC files

This is not yet possible, but Thomas Krijnen, the guy behind IfcOpenShell is working on it, so very likely Blender and FreeCAD will be able to output IFC files in some near future.